Lead author Dr Andrea Fortini said: “When coatings such as paint, ink or even outer layers on tablets are made, they work by spreading a liquid containing solid particles onto a surface, and allowing the liquid to evaporate.

"This is nothing new, but what is exciting is that we’ve shown that during evaporation, the small particles push away the larger ones, remaining at the top surface while the larger are pushed to bottom. This happens naturally.

“This type of ‘self-layering’ in a coating could be very useful. For example, in a sun screen, most of the sunlight-blocking particles could be designed to push their way to the top, leaving particles that can adhere to the skin near the bottom of the coating.

"Typically the particles used in coatings have sizes that are 1000 times smaller than the width of a human hair so engineering these coatings takes place at a microscopic level."

The findings have been published in the journal Physical Review Letters with the catchy title 'The science of watching paint dry; nanotech for everyday impact'.